Liquid-Liquid Separator Interface Detection System and Polymerization Process Utilizing the Same

ABSTRACT

A system for detecting an interface between a polymer-rich phase and a solvent-rich phase comprising a liquid-liquid separator configured to receive a polymer solution as an inlet stream comprising solvent, polymer and unreacted monomer produced in a solvent-based polymerization reactor through an inlet feed, wherein a tank is configured to provide a residence time of at least 20 minutes and to permit the stream to separate into the polymer rich phase and the solvent rich phase; a first sonic transponder for sending a first sonic signal from either a top or bottom of the liquid-liquid separator and for receiving a first reflected portion of the sonic signal, the reflected portion of the sonic signal created by the passage of the sonic signal through a liquid-liquid interface between the solvent rich phase and the polymer rich phase, wherein the first sonic transponder is positioned such that it transmits the signal which travels perpendicularly to the liquid-liquid interface is provided.

FIELD OF INVENTION

The instant invention relates to a liquid-liquid separator interfacedetection system and polymerization process utilizing same.

BACKGROUND OF THE INVENTION

Liquid-liquid separators are used in a variety of applications toseparate two liquid phases having different densities. Liquid-liquidseparators may be used to separate the solvent and polymer in theSolution Polyolefin process. For the stability of a solution, it is veryimportant to control the interface layer (the rag layer) between thepolymer solution and pure solvent. The location of this layer determinesthe degree of separation between the two liquids. Unfortunately, theseparator does not contain any side glass to view the interface and asonic probe was used to detect the polymer and solvent interface in thecarbon steel vessel.

SUMMARY OF THE INVENTION

The instant invention is a liquid-liquid separator interface detectionsystem and polymerization process utilizing same.

In one embodiment, the instant invention provides a system for detectingan interface between a polymer-rich phase and a solvent-rich phasecomprising a liquid-liquid separator (LLS) configured to receive aninlet stream comprising solvent, polymer and unreacted monomer producedin a solvent-based polymerization reactor through an inlet feed, whereinthe tank is configured to provide a residence time of at least 20minutes and to permit the stream to separate into a polymer rich phaseand a solvent rich phase; a first sonic transponder for sending a firstsonic signal from either a top or bottom of the liquid-liquid separatorand for receiving a first reflected portion of the sonic signal, thereflected portion of the sonic signal created by the passage of thesonic signal through a liquid-liquid interface between the solvent richphase and the polymer rich phase, wherein the first sonic transponder ispositioned such that it transmits a signal with travels perpendicularlyto the liquid-liquid interface.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there is shown in thedrawings a form that is exemplary; it being understood, however, thatthis invention is not limited to the precise arrangements andinstrumentalities shown.

FIG. 1 is a schematic of a liquid-liquid separator with two sonictransponders according to an embodiment of the invention; and

FIG. 2 is a graph demonstrating the changes of solution densities of thesolvent rich and polymer rich phases as a function of separation agentconcentration upon the occurrence of liquid-liquid separation, and theability of the sonic transponder to detect the presence of a liquidliquid interface between the two phases upon the formation of two liquidphases.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention is a liquid-liquid separator interface detectionand control system and polymerization process utilizing same.

The liquid-liquid separator interface detection system according to thepresent invention comprises: a liquid-liquid separator (LLS) configuredto receive polymer solution as an inlet stream comprising solvent,polymer and unreacted monomer produced in a solvent-based polymerizationreactor through an inlet feed, wherein the tank is configured to providea residence time of at least 20 minutes and to permit the stream toseparate into a polymer rich phase and a solvent rich phase; a firstsonic transponder for sending a first sonic signal from either a top orbottom of the liquid-liquid separator and for receiving a firstreflected portion of the sonic signal, the reflected portion of thesonic signal created by the passage of the sonic signal through aliquid-liquid interface between the solvent rich phase and the polymerrich phase, wherein the first sonic transponder is positioned such thatit transmits a signal with travels perpendicularly to the liquid-liquidinterface.

Liquid-liquid separator systems generally of use in embodiments of theinvention are generally described in U.S. Patent Application PublicationNo. 20120088893, the disclosure of which is incorporated herein byreference. As discussed therein, a liquid-liquid separator may be usedto remove solvent from polymer solution by using the phenomenon of LowerCritical Solution Temperature (LCST) in the solution polymerizationprocess. The present invention relates to the use of a sonic transponderto detect the location of the liquid-liquid interface between thepolymer-rich phase and the solvent-rich phase.

The polymerization process according to the instant invention comprises:A) polymerizing one or more monomers in the presence of a reactionsolvent, to form a polymer solution; B) transferring the polymersolution as an inlet stream into a liquid-liquid separator, withoutadding heat to the solution, and wherein the pressure of the polymersolution is actively reduced in a controlled manner prior to, or within,the liquid-liquid separator, to induce at least two liquid phases, apolymer-rich phase and a solvent-rich phase, and wherein theconcentration of polymer in the polymer-rich phase is higher than thatin the polymer solution transferred to the liquid-liquid separator; andC) detecting an interface between the polymer-rich phase and thesolvent-rich phase by use of a sonic transponder positioned within theliquid-liquid separator; and D) removing one or both of the solvent-richphase and the polymer-rich phase.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat polymer solution has a residence time in the LLS of at least 20minutes. All individual values and subranges from at least 20 minutesare included herein and disclosed herein; for example, the residencetime can be from a lower limit of 20, 24, 28, 32, 36, or 40 minutes. Forexample, the residence time may be from at least 20 minutes, or in thealternative, the residence time may be from at least 30 minutes or inthe alternative, the residence time may be from at least 40 minutes. Theresidence time is the average amount of time a fluid (typically twophases) spends in the LLS. This time is calculated as the ratio of the“volume of the LLS vessel”/“volumetric flow rate of the inlet streaminto the LLS.”

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the first sonic transponder is enclosed partially in a sleeve. Insuch embodiments, the sleeve is configured and placed so that it doesnot interrupt or impact the path of the soundwave generated by the sonictransponder.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the inlet feed feeds the polymer solution into a bottom portion ofthe liquid-liquid separator.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator is jacketed.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator is a gravity separator.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the system further comprises a polymer rich phase outlet valvecomprising a flow meter and a differential pressure transmitter locatedon either side of the flow meter.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the system further comprises an automated control valve to controlthe level of polymer rich phase in the liquid-liquid separator.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the system further comprises a second sonic transponder for sendinga second sonic signal from either a top or bottom of the liquid-liquidseparator and for receiving a second reflected portion of the sonicsignal.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the system further comprises a control system to receive andanalyze data recovered from the first, and optionally from the second,sonic transponders.

Sonic transponders and control systems therefore are known in the artand are commercially available. One exemplary commercially availablesonic transponder and control system is available under the trade nameINTERFAZER from Transducer USA (Houston, Tex.).

As used herein, the term “sonic transponder” means a device includingboth a sound transmitter and a sound receiver. Sonic transponders areuseful in the inventive system and process and are based on theprinciples of active SONAR. Active sonar creates a pulse of sound, asoundwave, and then detects reflections of the pulse. This pulse ofsound is generally created electronically using a sonar projectorconsisting of a signal generator, power amplifier and electro-acoustictransducer/array. A beamformer may be employed to concentrate theacoustic power into a beam. A portion of the sound wave is reflectedfrom an interface between two liquid phases having different densitiesor between liquid and solid phases. The reflected portion is received bythe sonic transponder and the distance to the interface may becalculated using known principles based on the speed of sound inliquids. Commercial systems, such as the INTERFAZER, typically includethe standard electronics and software for converting reflected soundwaves into electronic signals and for calculating the location of theinterface which generated a reflected sound wave.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the sonic transponder provides continuous interface detection.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the sonic transponder provides intermittent interface detection. Insuch embodiments, the sonic transponder may send and receive signals atspecified time intervals or on demand.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the reaction solvent is a mixture of a heavy hydrocarbon solvent(for example, containing a C₆-C₁₀ hydrocarbon component) and a lighthydrocarbon solvent (for example, containing a C₂-C₅ hydrocarboncomponent). The liquid-liquid separation can be achieved by droppingpressure, thereby inducing the formation of two phases, polymer-rich andsolvent-rich liquid phases.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the heavy hydrocarbon solvent comprises at least one hydrocarboncontaining from 6 to 10 carbon atoms. In an alternative embodiment, theat least one hydrocarbon can comprise at least one hydrocarboncontaining from 7 to 9 carbon atoms.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the heavy hydrocarbon solvent does not comprise a hydrocarboncontaining less than 6 carbon atoms, although residual amounts(typically less than 10000 ppm, based on total weight of heavyhydrocarbon solvent) of such hydrocarbons may be present. A“hydrocarbon,” as used herein refers to an organic molecule made up ofonly carbon and hydrogen atoms.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the light hydrocarbon solvent comprises at least one hydrocarboncontaining from 2 to 5 carbon atoms. In one embodiment, the lighthydrocarbon solvent comprises at least one hydrocarbon containing from 2to 4 carbon atoms.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the light hydrocarbon solvent does not comprise a hydrocarboncontaining more than 5 carbon atoms, although residual amounts(typically less than 10000 ppm, based on total weight of lighthydrocarbon solvent) of such hydrocarbons may be present. A“hydrocarbon,” as used herein refers to an organic molecule made up ofonly carbon and hydrogen atoms.

In one embodiment, the light hydrocarbon solvent is selected fromethane, propane, isobutane, or isopentane, or mixtures thereof, andpreferably propane or isobutane.

In one embodiment, the amount of light hydrocarbon solvent is from 5 to40 weight percent, based on the weight of the polymer solution. Allindividual values and subranges from 5 to 40 weight percent are includedherein and disclosed herein; for example, the amount of lighthydrocarbon solvent in the polymer solution can be from a lower limit of5, 15, 25 or 35 weight percent to an upper limit of 10, 20, 30 or 40weight percent. For example, the amount of light hydrocarbon solvent inthe polymer solution may be in the range of from 5 to 40 weight percent,or in the alternative, the amount of light hydrocarbon solvent in thepolymer solution may be in the range of from 20 to 35 weight percent.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the heavy hydrocarbon solvent is selected from n-hexane, n-heptane,n-octane, iso-octane, n-nonane, n-decane, or mixtures thereof,preferably n-octane, iso-octane, n-nonane, n-decane, or mixturesthereof, and more preferably n-octane.

In one embodiment, the solvent comprises from 20 to 50 weight percentbased on the sum weight of the light hydrocarbon solvent and the heavyhydrocarbon solvent. All individual values and subranges from 20 to 50weight percent are included herein and disclosed herein; for example,the amount of light hydrocarbon solvent based on the sum weight of thelight hydrocarbon solvent and the heavy hydrocarbon solvent can be froma lower limit of 20, 30, or 40 weight percent to an upper limit of 25,35, 45, or 50 weight percent. For example, the amount of lighthydrocarbon solvent based on the sum weight of the light hydrocarbonsolvent and the heavy hydrocarbon solvent may be in the range of from 20to 50 weight percent, or in the alternative, from 20 to 40 weightpercent.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the light hydrocarbon solvent comprises a C3 hydrocarbon, and theheavy hydrocarbon solvent comprises a hydrocarbon with 8 or more carbonatoms.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the light hydrocarbon solvent comprises a C3 hydrocarbon, and theheavy hydrocarbon solvent comprises a hydrocarbon with 10 or more carbonatoms.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat there is no special operation (like distillation), in thepolymerization process, to separate heavy and light hydrocarboncomponents of the solvent from each other.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat there is no special unit operation (such as distillation), in thepolymerization process, to separate the solvent from the monomers andco-monomers.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat there is no special unit operation (such as distillation), in thepolymerization process, to separate the solvent from the polymers.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat, in step B, the polymer concentration in the polymer solutionentering the liquid-liquid separator is from 5 to 30 weight percent,based on the weight of the polymer solution. All individual values andsubranges from 5 to 30 weight percent of the polymer solution areincluded herein and disclosed herein; for example, the polymerconcentration in the polymer solution can be from a lower limit of 5,15, or 25 weight percent to an upper limit of 10, 20 or 30 weightpercent. For example, the polymer concentration in the polymer solutionmay be in the range of from 5 to 30 weight percent, or in thealternative, the polymer concentration in the polymer solution may be inthe range of from 10 to 15 weight percent, or in the alternative, thepolymer concentration in the polymer solution may be in the range offrom 15 to 20 weight percent.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat, in step B, the polymer concentration in the polymer in thepolymer-rich phase exiting the liquid-liquid separator is from 20 to 50weight percent. All individual values and subranges from 20 to 50 weightpercent are included herein and disclosed herein; for example, thepolymer concentration in the polymer in the polymer-rich phase exitingthe liquid-liquid separator can be from a lower limit of 20, 30, 40 or45 weight percent to an upper limit of 25, 35, 45 or 50 weight percent.For example, the polymer concentration in the polymer in thepolymer-rich phase exiting the liquid-liquid separator may be in therange of from 20 to 50 weight percent, or in the alternative, thepolymer concentration in the polymer in the polymer-rich phase exitingthe liquid-liquid separator may be in the range of from 35 to 50 weightpercent, or in the alternative, the polymer concentration in the polymerin the polymer-rich phase exiting the liquid-liquid separator may be inthe range of from 20 to 35 weight percent, or in the alternative, thepolymer concentration in the polymer in the polymer-rich phase exitingthe liquid-liquid separator may be in the range of from 30 to 40 weightpercent.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat no heat is added between each reactor and the liquid-liquidseparator.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the process does not contain a heating device, such as a heatexchanger between step A and step B.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat no heat is added to the polymer solution in step A and step B, bymeans of a heat exchanger.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat no heat is added to the polymer solution in step A and step B, bymeans of a higher temperature stream (higher energy).

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat step B is not repeated.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat step B is repeated.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat, in step B, the polymer solution forms only two liquid phases.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat, no light hydrocarbon solvent is added to step B.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat, light hydrocarbon solvent is added to step B.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat one or more phase separation agents are added to the polymersolution prior to, or within, the liquid-liquid separator.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat no phase separation agent is added to the polymer solution priorto, or within, the liquid-liquid separator. In a further embodiment, nophase separation agent is added to the polymer solution after theliquid-liquid separator.

Some examples of phase separation agents include H₂, N₂, CO, CO₂, C₃H₈and CH₄.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the polymer-rich phase does not contain more than 5 weight percententrained “solvent-rich phase,” based on sum weight of these two phases.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat, in step B, the pressure in the liquid-liquid separator is lessthan, or equal to, 800 psig. All individual values and subranges fromless than, or equal to, 800 psig are included herein and disclosedherein; for example, the pressure in the liquid-liquid separator can befrom an upper limit of 800 psig. For example, the pressure in theliquid-liquid separator can be from an upper limit of 700 psig, or inthe alternative, the pressure in the liquid-liquid separator can be froman upper limit of 600 psig.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat, in step B, the pressure in the liquid-liquid separator is from 400psig to 800 psig.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the pressure in the liquid-liquid separator is from 450 psig to 700psig.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the pressure in the liquid-liquid separator is from 500 psig to 600psig.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the temperature in the liquid-liquid separator is greater than, orequal to, 150° C. All individual values and subranges from greater than,or equal to, 150° C. are included herein and disclosed herein. Forexample, the temperature in the liquid-liquid separator can be from anupper limit of 150° C., or in the alternative, the temperature in theliquid-liquid separator can be from an upper limit of 160° C., or in thealternative, the temperature in the liquid-liquid separator can be froman upper limit of 170° C.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat, in step B, the temperature in the liquid-liquid separator is from150° C. to 220° C.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the temperature in the liquid-liquid separator is from 160° C. to210° C.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the temperature in the liquid-liquid separator is from 165° C. to205° C.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator is a vessel.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator has a capacity greater than, or equalto, 10 gallons.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator has a capacity greater than, or equalto, 100 gallons.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator has a capacity greater than, or equalto, 1000 gallons.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator has a capacity greater than, or equalto, 10,000 gallons.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator has a capacity greater than, or equalto, 50,000 gallons.

In one embodiment, the liquid-liquid separator has a capacity from 10 to50,000 gallons. In one embodiment, the liquid-liquid separator has acapacity from 100 to 25,000 gallons. In a preferred embodiment, nomechanical mixing takes place in the liquid-liquid separator.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the liquid-liquid separator, in step B, contains at least twoliquid phases. A liquid phase has a density greater than, or equal to,0.2 g/cc, preferably greater than, or equal to, 0.3 g/cc, as determinedgravimetrically.

The liquid-liquid separator may comprise a combination of two or moreembodiments as described herein.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the solvent-rich phase comprises less than 1000 ppm polymer. Allindividual values and subranges from less than 1000 ppm polymer areincluded herein and disclosed herein; for example, the amount of polymerin the solvent rich phase can be from an upper limit of 250, 350, 450,550, 650, 750, 850, 950, or 1000 ppm.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat step (A) occurs in a solution polymerization reactor.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat step (A) occurs in a continuously stirred tank reactor.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the polymerization process further comprises calculating a verticalposition of the interface face from a reflected sonic signal received bythe sonic transponder.

In an alternative embodiment, the instant invention provides aliquid-liquid separator interface detection system and polymerizationprocess, in accordance with any of the preceding embodiments, exceptthat the polymerization process further comprises adjusting a flow rateby removing one or both of the solvent-rich and the polymer-rich phasesbased upon the vertical position of the interface.

FIG. 1 is a schematic of a liquid-liquid separator 1 having two sonictransponders, 2 and 4. The liquid-liquid separator 1 includes a solventrich phase 6 and a polymer rich phase 8. As shown in FIG. 1, the sonictransponders 2 and 4 are each positioned such that the sound wave fromeach transponder is at a right angle to the liquid-liquid interface.Polymer solution from a polymerization reactor enters the liquid-liquidseparator 1 through inlet 10.

The term “polymer,” as used herein, refers to a polymeric compoundprepared by polymerizing monomers, whether of the same or a differenttype. The generic term polymer thus embraces the term homopolymer(employed to refer to polymers prepared from only one type of monomer),and the term interpolymer as defined hereinafter. The term“interpolymer,” as used herein, refers to polymers prepared by thepolymerization of at least two different types of monomers. The genericterm interpolymer thus includes copolymers (employed to refer topolymers prepared from two different types of monomers), and polymersprepared from more than two different types of monomers.

The term “olefin-based polymer,” as used herein, refers to a polymerthat contains at least a majority weight percent, based on the weight ofthe polymer, polymerized olefin (for example, ethylene or propylene),and, optionally, one or more additional comonomers.

The term “ethylene-based polymer,” as used herein, refers to a polymerthat contains at least a majority weight percent polymerized ethylene(based on the weight of polymer), and, optionally, one or moreadditional comonomers.

The term “propylene-based polymer,” as used herein, refers to a polymerthat contains at least a majority weight percent polymerized propylene(based on the weight of polymer), and, optionally, one or moreadditional comonomers.

The term “polymer-rich phase,” as used herein, in relation to two ormore phases under consideration, refers to the phase containing thegreater concentration of polymer, as measured by its weight fraction,based on the total weight of the polymer-rich phase.

The term “solvent-rich phase,” as used herein, in relation to two ormore phases under consideration, refers to the phase containing thegreater concentration of solvent as measured by its weight fraction,based on total weight of the solvent-rich phase.

The term “heavy hydrocarbon solvent,” as used herein, refers to anon-reactive (with respect to polymerization catalyst) hydrocarbon,containing at least one hydrocarbon containing six or more carbon atoms.Typically, heavy hydrocarbon solvents have a normal boiling point higherthan 95° C. The heavy hydrocarbon solvent does not comprise ahydrocarbon containing less than six carbon atoms, although residualamounts (typically less than 10000 ppm, based on total weight of heavyhydrocarbon solvent) of such hydrocarbons may be present. A“hydrocarbon,” as used herein refers to an organic molecule made up ofonly carbon and hydrogen atoms. Examples are alkanes like n-octane,n-nonane, iso-octane, and alkenes like internal isomers of octene (thosewith double bond not located on a terminal carbon atom).

The term “light hydrocarbon solvent,” as used herein, refers to anon-reactive (with respect to polymerization catalyst) hydrocarbon,containing at least one hydrocarbon containing five or less carbonatoms. Typically, light hydrocarbon solvents have a normal boiling pointlower than 40° C. The light hydrocarbon solvent does not comprise ahydrocarbon containing more than five carbon atoms, although residualamounts (typically less than 10000 ppm, based on total weight of lighthydrocarbon solvent) of such hydrocarbons may be present. A“hydrocarbon,” as used herein refers to an organic molecule made up ofonly carbon and hydrogen atoms. Examples include ethane, propane,isobutene, and the like.

A phase, as used herein, refers to is a region of space (a thermodynamicsystem), throughout which all physical properties of a material areessentially uniform. Examples of physical properties include density,index of refraction, and chemical composition.

A liquid-liquid phase is a combination of two separate liquid phaseswhich are not miscible.

The term “liquid-liquid separator (LLS),” as used herein, refers to adevice used for the separation of two or more liquid phases. Theseparation results from the specific action, for example, a reduction inpressure, taken to induce two or more liquid phases.

The term “polymer solution,” as used herein, refers to the completedissolution of polymer in one or more solvents (typically much lower inmolecular weight than polymer) to form a homogeneous (most often inliquid state) phase. The solution comprises the polymer and solvent, andmay also comprise unreacted monomers and other residuals of thepolymerization reaction.

The term “solvent,” as used herein, refers to a substance (for example,a hydrocarbon or a mixture of two or more hydrocarbons (excludingmonomer and comonomer)) that dissolves a species of interest, like amonomer and/or polymer, resulting in a liquid phase.

The term “mixed solvent,” as used herein, refers to a mixture of two ormore solvents (for example, a mixture of two or more hydrocarbons).

The term “single solvent,” as used herein, refers to one solvent (forexample, one hydrocarbon).

The term “solution polymerization,” as used herein, refers to apolymerization process in which the formed polymer is dissolved in thepolymerization solvent.

The term “phase separation agent,” as used herein, refers to asubstance, which, when added to an existing polymer solution, has theeffect of lowering the Lower Critical Solution Temperature (LCST) at agiven polymer weight fraction.

Lower Critical Solution Temperature (LCST), as used herein, is definedas the temperature, above which, a solution of fixed composition, at afixed pressure, separates into two liquid phases, and, below thistemperature, the solution exists as a single liquid phase.

The term “polymerization system,” as used herein, refers to a mixturecomprising monomers, solvent and catalyst, and which will undergopolymerization reaction under appropriate conditions. The polymerizationsystem corresponds to the total feed to the reactor.

The term “adiabatic reactor,” as used herein, refers to a reactor whichhas no active heat removal mechanism and no active heat additionmechanism.

The term “pressure reducing means,” as used herein, refers to a device,such as a control valve, that allows reduction in pressure of acontinuous stream of liquid or a fixed batch of liquid.

The phrase “actively reduced in a controlled manner,” as used herein,refers to an action, such as the use of a control valve, to reducepressure to a desired level and at a desired rate.

The term “single phase polymer solution,” as used herein, refers to thecomplete dissolution of polymer in one or more solvents (typically muchlower in molecular weight than polymer) to form a homogeneous (mostoften in liquid state) phase.

The phrase “concentration of polymer in the polymer-rich phase,” as usedherein, refers to the weight fraction of the polymer, based on the totalweight of the solution containing the polymer (polymer-rich phase).

The phrase “concentration of polymer in the solvent-rich phase,” as usedherein, refers to the weight fraction of the polymer, based on the totalweight of the solution containing the polymer (solvent-rich phase).

The term “subcritical region,” as defined herein, refers to apolymerization temperature below the critical temperature of thepolymerization medium (defined as the mixture of solvent(s), monomer andcomonomer(s) [no catalyst(s) or cocatalyst(s)]), and a polymerizationpressure below the critical pressure of the polymerization medium.

The term “critical temperature,” as used herein, refers to thetemperature of the polymerization medium, above which, thepolymerization medium does not phase separate, regardless of anypressure change.

The term “critical pressure,” as used herein, refers to the pressure ofthe polymerization medium, above which, the polymerization medium doesnot phase separate, regardless of any temperature change.

The term “cloud point pressure” is the pressure, below which, thepolymer solution of a fixed composition at a fixed temperature,separates into two liquid phases. Above this pressure, the polymersolution is a single liquid phase.

“Cloud point temperature” is the temperature above (thresholdtemperature) which, the polymer solution of a fixed composition at afixed pressure, separates into two liquid phases. Below thistemperature, the polymer solution is a single liquid phase. In addition,the cloud point temperature may also be a ceiling temperature, belowwhich, two phases exist, and above which, one phase exists.

EXAMPLES

The following examples illustrate the present invention but are notintended to limit the scope of the invention. FIG. 2 illustrates theseparation of a solvent rich phase and a polymer rich phase, as detectedby an INTERFAZER sonic transponder. The polymer solution from a singlesolution continuously stirred reactor for production of asemi-crystalline, very low diene-containing ethylene-propylene-dieneterpolymer (EPDM) was used to produce the information in FIG. 2. Highreactor pressure was used to ensure a single liquid phase environmentfor homogeneous polymerization. The pressure of the polymer solution wasquickly reduced from 2200 psig to 800 psig as the polymer solutionpassed through the reactor pressure control valve. The resulting densityof the polymer-rich stream after liquid-liquid separation was predicted,using VXLE modeling software from VXLE ApS (Copenhagen, Denmark) to be35.5 lbs/ft³ at 185° C. and 783 psig with a solution densitydifferential between the polymer rich and solvent rich phases of 9lbs/ft³. FIG. 2 shows the phase separation as a function of time andphase separation agent concentration. On FIG. 2, the far left positionindicates the start time for injection of a phase separation agent. Atthat point, the densities of the polymer rich phase and the solvent richphase are very close to each other and to the reactor effluent (polymersolution) density. Propane, a separation agent, is fed into theliquid-liquid separator beginning at the time indicated by the far leftof the y-axis. As the propane concentration in the liquid-liquidseparator increases, the solution density of the solvent rich phasedecreases. At a propane concentration of 13%, the solvent rich phaseshows a rapid decrease in density. At that same propane concentration,the sonic transponder shows a 40 to 50% liquid liquid interface level(“1^(st) big density drop”). Upon reaching 15% propane, propane levelwas maintained constant during which time the density difference wasmaintained and the sonic transponder showed a clear interface.Subsequently, the propane was removed. Upon dropping below 13% propane,the viscosities of the polymer rich and solvent rich phases approachedeach other and the sonic transducer did not show clear phase separation.In FIG. 2, the long dashed line indicates the polymer rich phasedensity, the dash-dot-dash line indicates the solvent rich phasedensity, the solid line indicates the propane content, and the sonictransponder signal is indicated by the dotted line.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicating the scope of the invention.

1. A system for detecting an interface between a polymer-rich phase anda solvent-rich phase comprising: a liquid-liquid separator configured toreceive an inlet stream comprising solvent, polymer and monomer producedin a solvent-based polymerization reactor through an inlet feed, whereinthe tank is configured to provide a residence time of at least 20minutes and to permit the stream to separate into the polymer rich phaseand the solvent rich phase; a first sonic transponder for sending afirst sonic signal from either a top or bottom of the liquid-liquidseparator and for receiving a first reflected portion of the sonicsignal, the reflected portion of the sonic signal created by the passageof the sonic signal through a liquid-liquid interface between thesolvent rich phase and the polymer rich phase, wherein the first sonictransponder is positioned such that it transmits a signal with travelsperpendicularly to the liquid-liquid interface.
 2. The system accordingto claim 1, further comprising a sleeve partially or wholly enclosingthe first sonic transponder.
 3. The system according to claim 1, whereinthe inlet feed feeds the stream into a bottom portion of theliquid-liquid separator.
 4. The system according to claim 1, wherein theliquid-liquid separator is jacketed.
 5. The system according to claim 1,wherein the liquid-liquid separator is a gravity separator.
 6. Thesystem according to claim 1, further comprising a polymer rich phaseoutlet valve comprising a flow meter and a differential pressuretransmitter located on either side of the flow meter.
 7. The systemaccording to claim 1, further comprising an automated control valve tocontrol the level of polymer rich phase in the liquid-liquid separator.8. The system according to claim 1, further comprising a second sonictransponder for sending a second sonic signal from either a top orbottom of the liquid-liquid separator and for receiving a secondreflected portion of the sonic signal.
 9. The system according to claim1, further comprising a control system to receive and analyze datarecovered from the first, and optionally from the second, sonictransponders.
 10. A polymerization process comprising: A) polymerizingone or more monomers in the presence of a solvent, to form a polymersolution; B) transferring the polymer solution to a liquid-liquidseparator, without adding heat to the solution, and wherein a pressureof the polymer solution is actively reduced in a controlled manner priorto, or within, the liquid-liquid separator, to induce at least twoliquid phases, a polymer-rich phase and a solvent-rich phase, andwherein a concentration of polymer in the polymer-rich phase is higherthan that in the polymer solution transferred to the liquid-liquidseparator; and C) detecting an interface between the polymer-rich phaseand the solvent-rich phase by use of a sonic transponder positionedwithin the liquid-liquid separator; and D) removing one or both of thesolvent-rich phase and the polymer-rich phase.
 11. The polymerizationprocess according to claim 10, wherein the solvent-rich phase is removedfrom the liquid-liquid separator and the removed solvent-rich phasecomprises less than 1000 ppm polymer.
 12. The polymerization processaccording to claim 10, wherein step (A) occurs in a solutionpolymerization reactor.
 13. The polymerization process according toclaim 10, wherein step (A) occurs in a continuously stirred tankreactor.
 14. The polymerization process according to claim 10, furthercomprising calculating a vertical position of the interface face from areflected sonic signal received by the sonic transponder.
 15. Thepolymerization process according to claim 10, further comprisingadjusting a flow rate of removing one or both of the solvent-rich andthe polymer-rich phases based upon the vertical position of theinterface.